Twenty-four hours later, we can be pretty sure that of “smoking guns” in the leaked CRU documents there are none. Everyone can read that information any way they please, as evidence of a global conspiracy or demonstration that climate science is solid and honest.

Whatever…now there’s a little bit more people aware that Science is done by humans, with their preferences and dislikes, their personal beliefs, and capable to use all the tricks of “power politics” to isolate opponents and to support friends. At the end of the day, the problem is not much in scientists that have an “ideology of science”. There’s plenty of it in history, from the controversy about the wave-particle nature of light to the patriotic debates about who invented calculus.

The problem is with scientists whose ideology involves stifling debate and censoring those who do not follow orthodoxy.

Let’s just hope there will be less of that…especially because the alternative is the piling up of yet more revelations, transforming it all in some kind of “climate tabloid journalism”.

This is the fifth and final posting in a series analyzing the information that can be obtained from the available HadCRUT data up to December 2007.

In summary: the world does appear to have warmed (but by the same token, it has cooled considerably during the year 2007). There are strong indications that it has been a very much hemispheric phenomenon, with little seasonality and hence minimal if any contribution from CO2. Likely culprits are therefore hemispheric-wide effects, such as those caused by the Sun and land use.

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Note that the HadCRUT data has just been updated to January 2008, with the following anomalies:

TWO ISSUES I WILL NOT DISCUSS HERE: (a) the meaning of using 3 decimal digits; (b) the meaning of obtaining a Global sea-surface temperature value simply as the arithmetic mean of Northern’s and Southern Hemisphere’s

In HadCRUT Data Rank Analysis (II) the 2007 monthly temperature averages are shown as having broken only one record (January’s, for Land/Northern Hemisphere), with rankings getting higher and higher over the year reaching as much as #34 for December/Sea surface/Southern Hemisphere).

In HadCRUT Data Rank Analysis (III) a plot of the yearly temperature averages’ rankings shows a clustering of warm years in the past couple of decades, although most graphs have a “capped” shape suggesting the maximum values have already been reached, at least for now. The steepest gradient in terms of rankings is by the way between 1910 and 1938, again suggesting we may be experiencing just the upper end of a temperature peak. Finally, graphs are much similar intra-then inter-hemispheric (Land NH looks much more like Sea NH than Land SH).

In HadCRUT Data Rank Analysis (IV), the analysis moves a step further by comparing seasons. Correlations can be divided in three groups: Land/Sea, same hemisphere (between 80% and 98.6%, in all seasons); Season-to-following-Season (between 71% and 80.5%, land/sea, all hemispheres); and Season-to-Season (between 64.5% and 78.8%). In other words, there is a much weaker link between the ranking of, say, Northern and Southern Hemisphere Land Spring temperatures (intra-seasonal), than between the ranking of, say, Northern Land and Sea Spring temperatures (intra-hemispheric).

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The last result does not look obviously compatible with the theory that world-wide warming has been caused by CO2 and other so-called greenhouse gases. If that were true, the intra-seasonal correlations would be higher, as CO2 concentration has a strong seasonal component: instead, they are generally even lower than the link between, say, Winter temperatures to Spring temperatures.

The main variable to factor is in all evidence the hemisphere. Now, what can have an effect on sea and land temperatures all over a hemisphere, and in a different way all over the other hemisphere? First hypotheses could be the Sun, via some kind of different coupling with the Northern and Southern terrestrial hemispheres; or changes in land use, that do not have the same impact on land-rich NH compared to ocean-rich SH.

Climatology would be a very exciting science indeed, had it not been hijacked by people on a mission to save the world based on inexact data.

This is the fourth posting in a series analyzing the information that can be obtained from the available HadCRUT data, recently updated to December 2007.

As in the previous blogs, the focus is on rank analysis, since it is widely claimed that global warming can be discerned by the fact that most of the warmest years have occurred very recently.

It is actually possible to obtain a rough indication on what is behind the recorded warming in the HadCRUT data by going one step below the usual globe-averaged, year-averaged figures.

(a) A strong hemispheric component is already visible in the yearly averages of the month-by-month ranks:

Note how for example SST/Southern-hemisphere is much more similar to Land/Southern-Hemisphere than to SST/Northern-hemisphere.

(b) Similar considerations apply at a seasonal level. See the graphs for the January-March period:

Obviously the Jan-Mar period is Southern Summer and Northern Winter. Let’s have a look at the Summer-to-Summer plots then:

I have computed the same graphs for all quarters, and for all seasons.

(c) It always looks more important to be in the same hemisphere, rather than in the same season or the same surface.

But visual inspection may be misleading, so a good round of correlations is in order (for the sake of clarity, the full list is at the end of this entry). These are the results:

(d) Correlation is highest intra-hemispherically (that is, when, say, the Northern Hemisphere’s land temperatures have placed near the top ranks, the NH sea-surface temperatures too have done the same) with a maximum of 98.6% (Southern Hemisphere, local Autumn) and a minimum of around 80% (Northern Hemisphere, local Winter).

(e) Same-season correlations are among the lowest, with a maximum of 74.5% (Spring) and a minimum of 68.8% (Summer).

(f) Among all the season-to-following-season correlations, the lowest values belong to the Oct_Dec-Jan_Mar periods (between 71% for Land, Northern Hemisphere and 80.5% for Land, Southern Emisphere).

(g) There is little, or perhaps even none, appreciable difference between Land and Sea-surface results

Conclusions and working hypotheses for the future will be discussed in next blog in the series.

Let’s have a look now at the graphs for yearly averages, ranked from #0 (coldest) to #157 (warmest) for the period 1850-2007. Source is once again the HadCRUT data.

We are looking for trends, so instead of simply taking the published average temperatures for the year, I have averaged the monthly ranking for each year taken into consideration. There is anyway no considerable difference between the results of the two approaches.

Figure 1 above shows the rankings for the whole period. Things to note:

(a) There is a clustering of warmer years during the past 20 years or so. This does suggest an overall warming. Taking the HadCRUT data for good (otherwise there would be no point examining them), it is also possible to say that the “warmest X years happened within the past Y years”.

(b) The steepest gradient IN TERMS OF RANKING is by far between the cold years around 1910 and the warm years around 1938.

(c) All the graphs end up with a “cap”

To investigate point (c), Figure 2 above shows the rankings for the past 10 years. Things to note:

(d) Only Land/Northern-Hemisphere gives any indication of continuous warming to date.

(e) Temperatures in the Southern Hemisphere have not been warming on a decadal scale.

I have been notoriously bad at making predictions but on the basis of figures 1 and 2 it is plausible that at least for now, and at least everywhere but on Land/Northern-Hemisphere, temperatures have reached a high and may not increase further.

The following contains a list of warmest/coldest year, by data set and by month, plus the ranking for 2007 (where #1=warmest).

Among the values to note :

(a) The year 2007 has seen the warmest month of January since 1850 for Land/Northern Hemisphere and Land/Global. It also ranked second warmest for Sea-surface/Northern Hemisphere in January and February.

(b) For Sea-surface/Southern Hemisphere, November 2007 has been the 29th warmest, and December 2007 the 34th warmest. That is, they were quite cool compared to the maximum values, achieved in both cases in 1997. The same can be said for Sea-surface/Global, ranked #20 in December 2007.